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February 11, 2022 12 min read

This article needs a full revision. (Contradictory statements highlighted in red below)


EDIT: Accuracy. This exercise does not work the lower posterior chain. (Google: What is the posterior chain?)

EDIT: Formatting. Although this article is informative and interesting, there are large blocks of text that makes the article quite boring to read and make the readers eyes gloss over. A few bolded sentences acting as subheadlines to focus on important points would do this article well. (example below: The leg extension primarily activates the quads.) Note: the quads are not the posterior chain.

EDIT: All 'How To' or 'To-do' sentences need to be subheadlines, bolded and on their own line in every article. This creates some contrast for the eye as the reader scrolls.



Leg days should be made up of only the best exercises designed to target and train the leg muscles. Leg extensions are one of those exercises that isolate and activate your leg muscles for a toned and more muscular leg.

The leg extension is a basic quadriceps isolation movement that effectively builds the quads. Seeing that monster quads are challenging to develop, this isolation exercise is worth your time. Below, we have outlined why you need to perform leg extensions and do so in perfect form.

Leg extension in the simulator on quadriceps. 3D illustration

What Are Leg Extensions?

The leg extension, also known as knee extension, is an isolation exercise that focuses on engaging all the muscles of your lower posterior chain, especially the thigh muscles.

It takes a full range of various isolation exercises to target all four muscle groups in the thighs. Leg extensions are fundamental exercises that deserve a place on any gym-goer’s leg day workout session. It is a fundamental movement that is easy to learn and even easier to perform with perfect form. Like its name implies, leg extensions involve extending the legs straight out and folding them back to the initial starting position, all under the influence of a weighted padded bar. 

Do not be deceived by the simple look of this exercise. Leg extensions are beginner-friendly exercises that can be performed regardless of your fitness level. With this strength-training exercise, you need to use your legs to move the weighted pads on the machine. Although this might not look like much, it fires up a range of muscles from the entire length of your thighs to your ankle.

How To Do The Leg Extensions

To get the most out of your leg extensions, you must perfect your form during this exercise. What form? You might ask, given that you need to locate the nearest leg extension machine and settle right in. Like any other exercise, there are particular set rules you need to play by. These rules and tips would ensure that your form is perfect for the engagement of the necessary muscles.

It is also a key player in ensuring that you do not in any way or form suffer from injuries during this exercise. Essentially, performing leg extensions in perfect shape is for your benefit and safety. To begin leg extensions, start by selecting weight sizes that you can control comfortably for as long as 2-3 sets of the exercise. This would help you avoid cheat reps and lessen the stress on your muscles that might lead to muscle strains.

To do the leg extension:

  • Sit in the chair of the leg extension machine.
  • Keep your back straight and against the backseat.
  • Grip the side handles on each side of the chair
  • Place your feet behind the padded roller so that your shins come in contact with it.
  • If the padded roller does not lie just above your shin, you might need to adjust the chair to the correct height.
  • Engage your core.
  • Inhale and lift the padded roller away from you by moving your legs forward and extending them.
  • Stretch your feet forward until they are straight.
  • Once your legs are fully extended, hold this position for about three seconds. 
  • Squeeze your quads for the best effect
  • Gently lower your legs, bringing the bar back to the starting position.
  • This is one repetition. Repeat for as many reps as you can fit in a set.

There are no set rules for how many reps should be in a set or how many sets you need to complete. There is also no rule detailing the type of weight you should lift with your legs. This is all dependent on your health, comfort, current fitness level, and fitness goal. A great way to average out these factors is fitting in between 8-12 reps for a total of 3 steps.

Muscles Activated During Leg Extensions

The leg extension is a superb leg training exercise that targets the muscles of the leg, rewarding you with not only aesthetically pleasing legs but also strong legs. Legs are a big part of your workout time regardless of your level. A majority of your exercises are driven by leg power. Leg extensions help you strengthen these muscles that almost always seem to be underrated. Big buff thighs are a fad that can never fade. They contribute to that overall shredded look that many men thirst after. Big quads are a major-traffic stopper and significant flex that provides a bragging right at the gym. 

The leg extension primarily activates the quads.

The quads or quadriceps femoris muscle is not just one big slab of flesh that makes up the front and side of your thighs. It is divided into four parts or muscle groups named the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. These muscle groups help in movements that involve straightening the knees like running, walking, standing, or movements of the legs across its various planes. They bear the weight of the body and need to be strengthened in order to have better agility and mobility for both functional and sporting activities.

These muscles originate from the attachment of the femur to the hip. Due to this connection, the rectus femoris also assists in the hip's flexion. Together, the quads make up the most significant muscle in the body. Leg extensions also help activate and strengthen the patellar ligament and quadriceps knee attachment. The leg extension exercise works based on Torque force. Using a weight that rests close to your ankle joint, you push through your quads to straighten your knee.

Benefits Of Leg Extensions

The primary benefit of leg extensions is their ability to isolate, target, and strengthen the quad muscles. Unlike other exercises like the square, leg extensions focus on the quad muscles and are a great way to bulk up on your thighs. Strong quads are a great way to improve power output and athleticism. It strengthens the thighs, acting as a direct improvement in sports that require leg power like football, running, and cycling. 

Some benefits of leg extensions are:

  1. Functional strength: Not only are toned thighs the in-thing, but strong thighs are also a great way to boost your functional and athletic performances. Stronger thigh muscles provide better stability of the upper body and improved coordination. It provides an increased explosive start that makes you faster. The effect of leg extensions moves past the thigh muscles and extends to the connective tissues and ligaments that hold the muscles and connect them to the knee. This is thanks to the involvement of the knee joint in moving the resistance during leg extension exercises. 
  2. Prevent injuries: The strengthening of the thigh muscles and their ligaments goes a long way in preventing and reducing the risks of injuries. This is not only evident in functional activities but also in the workout and professional performance. Weaker thigh muscles have a higher risk of injuries, so strengthening them would help them become more durable and pliable enough for agility.
  3. Great foundation exercise:  Leg extensions are a great way to improve your performance at the gym. Exercises like heavy squats, jump squats, and tempo hamstring curls promise to provide leg strength and require a degree of leg strength to be performed. Leg extension tightens and strengthens your quads enough to help you scale up on other more challenging exercises. This would enable you to achieve your fitness goal even faster.
  4. Beginner-friendly: Leg extensions are beginner-friendly exercises. It doesn't matter if you haven't spent enough time in the gym to build strength; you can quickly learn to perform leg extensions in perfect form. Unlike other complex exercises that require discipline to hold proper workout posture, leg extensions are done using a machine. This helps them to easily adjust to and learn the appropriate way to carry out the exercise. With the machine taking care of everything about your posture, you simply need to focus on performing the exercise correctly.
  5. Isolation exercise: Isolation exercises are activities that help target and work for one muscle group at a time. They are the opposite of compound exercises like squats, which operate a wide range of different muscle groups. Leg extension as an isolation exercise helps you focus on building your thigh muscles. Unlike other leg exercises, you don't expend as much energy, and any energy that you do extend goes directly to stimulating your thigh muscles for hypertrophy.
  6. It is scalable: The leg extension is a scalable exercise, and the chances of you being stuck on a gain plateau are slim. With the adjustable weight available, you need to switch the light weight for a heavier option. 
  7. Rehab exercise: Leg extensions are a great way to treat the stiffness in your joints that arises from the lack of knee flexion under the influence of resistance.  Knee extension exercises are an excellent choice for after-surgery rehabilitation,so why is the leg extension exercise any different? Under the advice of a physician, the leg extension is a great way to retrain your quads, knees, and the involved ligaments after an injury or surgery. This is critical in helping you retain functional independence and hasten your return to athletic activities.
  8. Great finisher exercise: Although your leg day session might include a range of compound exercises, you might not get the best result without the inclusion of a finisher isolation exercise. Leg extensions provide that last needed isolated push on your thigh muscles. This encourages maximum muscle hypertrophy and gives you a bang for your buck after your general workout session.

Leg extensions are a superb option for you, depending on the fitness goal you wish to achieve. If you are looking for a way to tone, strengthen, and buff up your quads for massive thighs, you should consider doing leg extensions. It provides a great muscle pump that can complement ADABOLIC  for an increased muscle pump, improved vasodilation, better muscle endurance, and increased muscle hardness and fullness. 

Are you looking for a more defined physique without the massive bodybuilder thighs? Leg extensions can be used to tone your legs and build a layer of lean muscle for a better beach body. Skip leg extensions if too much stress on your knee joints leads to pain. If you are using leg extensions as a form of physical therapy, work with a personal trainer to help you avoid further injuries along the way.

Tips To Help You During Leg Extensions

Despite being a simple exercise, common mistakes can ruin a good leg extension workout. This can limit the contraction of your muscles and the equivalent muscle response needed for excellent output. Here are some tips to help you avoid these common mistakes.

  1. Don't lift too heavy: While you might be tempted to lift more heavily than you can handle, you should remember that this would put a strain on your knee joint. Before you load up the machine to the max weight, begin with a weight you are comfortable with and work your way up these sizes. These would ensure that you do not strain your knee joint too much and end up with an injury.
  2. Complement with other exercises: Over time, using leg extensions to focus on the front of your thighs would result in muscle imbalances. This would lead to an exaggerated thigh in contrast to undertrained calves. To avoid this, balance out leg extension exercises with a corresponding calf and hamstring exercise for equally trained legs. These exercises include calf raises, Good Mornings, Romanian deadlifts, and hamstring curls.
  3. Align your body: Avoid slouching or rounding your back during the leg extension. This will place a strain on your back, resulting in pressure in your back muscles. The stress, when left to go on for too long, can lead to back pain and increase your chances of back injury.
  4. Match the machine rotation and your knees: Knee position is crucial during leg extension. Ensure that the rotation axis of your knees and that of the machine are in sync. This will help you get the most out of your extensions without risking an overexpression on your knees. Do not put your knees too far behind or in front of the axis rotation to avoid putting stress on your knees and risking an injury.
  5. Point your toes: Pointing your toes will help you to get maximum contraction of the quads. This would also help to keep you focused.
  6. Work past failure: The strain in your quad should not be a marker as the end of your exercise. Instead, think of it as the beginning of your session. The strain signifies the ‘breakdown’ of your quad muscle fibers, a factor that shows that your muscle is getting adequate contraction for muscle hypertrophy. Work past muscle failure to get the most out of leg extensions.
  7. Contraction is necessary: Contraction of your quad muscles is essential to lock in the intensity of the exercise. Keep the contraction of your quads all through your workout.
  8. Take time off to recover: As much as your body needs exercise, it also needs time to rebuild and heal the broken down muscle fibers. This is vital for proper muscle growth and function. Take time off between each workout and ensure that you get adequate sleep. RESTED-AF can help you get better sleep and improve muscle recovery. Better sleep helps achieve better muscle fiber recovery and cognitive function for better focus. 

Leg Extension variations: 

1. Bodyweight Leg Extensions

Bodyweight leg extensions are great for firing up your quads. For this variation, you do not need any bulky gym equipment as your body weight, and gravity does all the work. It is a fantastic exercise choice for knee health and other complementary muscles. To do the bodyweight leg extension:

  • Kneel on the floor.
  • Keep your back straight and your neck neutral.
  • Your knees should be at a 90-degree angle with the floor.
  • Pre-tension your knees and squeeze your quads.
  • Tighten your core. Your body should form one straight line from your head to your knees.
  • Keep your back straight, lean back until you reach your limit.
  • Hold this position for a second.
  • Without slouching or using your hands for support, return to the standing position by keeping all the tension in your thighs.
  • Complete as many repetitions as possible.

Remember to warm up before you begin. To make this variation more challenging, place a resistance band behind your knees, and to make it easier, loop a resistance band around a sturdy object and use it for leverage. 

2. Standing Leg Extensions


    The standing leg extension is a beginner-friendly exercise. It offers the same benefits as a machine leg extension, but unlike the latter, standing leg extensions are a closed-chain exercise. This means that your supporting leg remains in a fixed position of constant contact with the floor. To do the standing leg extension:

    • Attach a cable or a resistance band to a sturdy object.
    • Fix the other end around your right ankle.
    • Stand close to the sturdy object, leaving little to no tension in the band.
    • Stand with your feet hip-width apart.
    • Keep your back straight and arms straight beside you.
    • Contract your core and pull your shoulders back. Put your hands on your hip for better balance.
    • Exhale and lift your right foot off the floor without moving any other part of your body.
    • Extend your knee fully out until you reach my limit.
    • Inhale and slowly return your right leg to the starting position.
    • This is one rep. Complete as many reps as you can fit in a set.

    To make the standing leg extension easier, support yourself by holding the wall or the back of a chair.

    3. Banded Leg Extension


      The banded leg extension is similar to the machine leg extension. The only difference is that you use a bench and a resistance band. The tension on your quads is not felt until you reach optimal stretch at the peak of your movement with your legs completely extended. To do the banded leg extension:

      1. Wrap one end of the resistance band around a sturdy object behind a bench.
      2. Sit on the bench and wrap the other end around your ankles.
      3. In the absence of a sturdy anchor, wrap one end of the ban around the leg of a short bench and sit on the extreme end of the bench.
      4. Keep your back straight and your knees at a 90-degree angle.
      5. Grip the bench for support if necessary.
      6. Slowly lift your feet off the floor, extending your knees.
      7. Pause at the peak of the movement.
      8. Slowly return your feet to the starting position.
      9. This is one repetition. Complete as many reps as you can fit in a set.

      Leg extension exercises can also be replaced or complemented with alternative exercises like Platz squats, front foot elevated Bulgarian split squat, close stance leg press, wall sits, and sissy squats. These exercises work the quads and provide equally great results.

      Working Your Quads

      Doing leg extensions is great for your quads. There are different variations you can add to your leg day workout routine. Leg extension shows evident benefits in your functional activities and the gym. It doesn't matter if it is as a starter exercise or a big finish to your leg sessions; ensure you add leg extensions to your workout routine. 

      Don't know where to begin your quad workouts from? Here are  ten additional quad exercises for you to try during your next workout!